Pressurized water nuclear reactors comprise components of large size such as steam generators which have a partly cylindrical outer casing of large diameter and very great height. This outer casing is usually constructed by butt welding cylindrical shells to each other or cylindrical shells to an annular assembly flange of a tube plate or a frustoconical shell.
Also mounted on the outer casing are, in the region of through openings of the casing, parts such as supports for the closing members for closing the inspection openings of the steam generator, nozzles or feed pipes of the steam generator. These mounted parts are welded on the casing of the steam generator in a joint region opening onto the outer surface of the casing.
The assembling and fixing welds for the mounted parts are produced from outside the casing of the steam generator.
The electron beam welding permits the production, without a filler metal, of welded joints of a very high metallurgical quality, with production times which are considerably reduced as compared with conventional techniques, for example arc welding.
However, one of the difficulties in carrying out the electron beam welding results from the need to establish a relatively high vacuum around the region of the connection of the parts onto which the electron beam is directed.
In the case of parts of modest size, it is possible to achieve the welding inside a fluidtight enclosure enclosing the electron gun in which the parts are introduced and placed in their position of assembly before the enclosure is closed in a fluidtight manner and evacuated.
It will be clear that, in the case of components of very large size such as steam generators, the cost of installations comprising fluidtight enclosures of very large size and the cost of the operation may become prohibitive.
Heretofore no process for electron beam welding parts of a component of large size such as a steam generator has been known which may be employed in a simple and rapid manner so as to limit the time required to manufacture the steam generator.
In particular, in the field of operations for replacing steam generators, rapid manufacturing processes may have to be available rapid manufacturing processs inasmuch as it is preferable to program the manufacture of the steam generators, which are extremely costly components, for precise utilizations. The replacement generators must be available within a well-defined and usually short period of time.